Reference will be made to the appended FIG. 1, which diagrammatically shows a top view of a spray bar suspension device of the state of the art.
In that figure, arrow A indicates the direction of travel of the agricultural vehicle E equipped with the device.
The suspension device comprises a stationary frame 1 secured on the vehicle E, a right bar holder 3 and a left bar holder 5 both pivotably mounted on the stationary frame 1, and right 7 and left 9 spray bars mounted stationary on said respective holders.
Right 11 and left 13 actuating cylinders, inserted between the stationary frame 1 and the respective holders 3, 5, make it possible to pivot said holders from a deployed position shown in FIG. 1, in which the two spray bars extend transversely to the direction of travel A and are thus ready for spraying, to a folded position, in which the two holders 3, 5 have pivoted toward the front of the vehicle, thereby placing the spray bars 7 and 9 in a direction substantially parallel to the direction of travel A.
This folded position in particular allows the agricultural vehicle to travel on the road.
A constant problem observed of the state of the art is the oscillating movement of the spray bars 7, 9, in particular in certain situations such as turns, braking and acceleration of the vehicle E: this is traditionally referred to as a “whiplash effect.”
These oscillations, which are particularly significant at the end of the bar given the considerable length of said bars, create very significant forces in the suspension device, which may break or deform the latter.
For that reason, different systems for damping these oscillations have been considered in the prior art.
Thus, in the device of FIG. 2, a slide 15 is inserted between the two cylinders 11 and 13, which can slide on the stationary frame while being returned to a central equilibrium position by elastic elements such as a spring 17. This device of the prior art allows pivoting with elastic return of the holders 3, 5 and therefore the associated bars 7, 9 both toward the front and the rear of the vehicle E, without phase lag.
In the device of the prior art shown in FIG. 3, compression springs 19, 21 are respectively inserted between the cylinders 11, 13 and the stationary frame 1.
These springs allow a rotation with elastic return of the bars 7, 9 only toward the rear of the vehicle E, with no phase lag.
The device of the prior art shown in FIG. 4 results from a combination of the two previous devices, and thus comprises not only a slide 15 elastically returned to its equilibrium position by the spring 17, but also compression springs 19 and 21 inserted between said slide 15 and the respective cylinders 11, 13.
This device of the prior art allows rotations of the bars 7, 9 both toward the front and the rear of the vehicle E, and a phase lag in the time of the oscillations of those two bars, in particular during turns, braking, acceleration of the vehicle E.